I was able to do a jump operation in the unity 2D action game development,
I kept jumping on the directional keys and jumped many times.
How can I make one jump when I press the arrow key once?

*Because I am a beginner to programming, I do not know how to change the operation key input. .. ..

If i keep pressing the arrow keys, you will repeatedly jump.

      // act when keyed
        float horizontalKey = Input.GetAxis("Horizontal");
        float verticalKey = Input.GetAxis("Vertical");
        float xSpeed ​​= 0.0f;
        float ySpeed ​​= -gravity;
        if (isGround)
        {
            if (verticalKey >0)
            {
                ySpeed ​​= jumpSpeed;
                jumpPos = transform.position.y;// record the jumped position
                isJump = true;
                jumpTime = 0.0f;
            }
            else
            {
                isJump = false;
            }
        }
        else if (isJump)
        {
            // Is the up arrow key pressed?
            bool pushUpKey = verticalKey>0;
            // Is the current height below the flight height
            bool canHeight = jumpPos + jumpHeight>transform.position.y;
            // Is the jump time too long?
            bool canTime = jumpLimitTime>jumpTime;
            if (pushUpKey&&canHeight&&canTime&&!isHead)
            {
                ySpeed ​​= jumpSpeed;
                jumpTime += Time.deltaTime;
            }
            else
            {
                isJump = false;
                jumpTime = 0.0f;
            }
        }

Key input method
if(Input.GetKeyDown("Jump"))
I also tried replacing it with
I got an error and it didn't work.

Please provide more detailed information here.